This invention relates to a format used for storing data in a memory storage disk and more specifically an optical storage disk. This invention also relates to an optical storage disk that contains both mastered and writeable areas.
Data storage disks, and in particular optical data storage disks, are widely used for a number of purposes. For example, downloading data via computer networks such as the Internet onto data storage disks is becoming increasingly popular. The downloaded data may include movies, music recordings, books, and other media. There are different types and sizes of data storage disks available for storing and accessing the downloaded information.
A number of benefits can be achieved using a data storage disk which can economically provide both mastered information and the ability to write or record information. As used herein, xe2x80x9cmastered informationxe2x80x9d refers to information in which content is incorporated (embossed) into the disk during the manufacture thereof. The information is typically represented by a series of pits or bumps in the reflective layer which alter the reflectivity of the layer and therefore can be detected by the read/write head as the track of pits or bumps passes beneath it. A common example of an optical disk is the well-known Compact Disc (CD), in which the information, normally music, is mastered prior to distribution.
A data storage device, e.g., a disk drive, which includes a read/write head is used to write information onto the disk and to read information from the disk. The disk drive is associated with a host device which uses the data read from the disk by the drive and which supplies data to be recorded by the disk drive onto the disk. A single host device may be coupled to more than one disk drive. Most prior art disk drives, including hard disk drives, floppy disk drives, and write once read many (WORM) disk drives (such as CD-R and DVD-R drives) are classified as xe2x80x9cblock levelxe2x80x9d devices. The drive itself simply reads or writes xe2x80x9cblocksxe2x80x9d of data pursuant to instructions from the host device, and is not concerned with the organization of the data blocks into files and directories.
Conventional storage disks assign specific areas for writing data files and for storing file system information or attributes (location, size, etc,) relating to the data files. This practice restricts the use of the disk. For example, a user who stores one large data file needs a relatively small area for storing file system information. In contrast, a user who stores numerous small data files requires proportionally more storage space for storing the file system information.
Conventional optical disk drives read and write data from an inner diameter (xe2x80x9cIDxe2x80x9d) of the disk towards an outer diameter (xe2x80x9cODxe2x80x9d) of the disk and at a constant linear track velocity. The data may be stored in a single spiral track formed about the center of the disk and the disk rotated in an angular direction such that a read/write head following the track moves outward towards the OD of the disk. Alternatively, the data may be stored in concentric circular tracks, in which case the read/write head xe2x80x9cjumpsxe2x80x9d outward to the next track after each rotation of the disk.
For example, a conventional CD has a first annular zone located near the ID of the disk that is reserved for a xe2x80x9ctable of contentsxe2x80x9d and a second annular zone located radially outward from the table of contents that is reserved for data. The data is written on a spiral track in a direction from the ID to the OD of the disk. Before any data can be read, the disk must be accelerated to a relatively high rotational velocity, using considerable power, so that the table of contents can be read. Moreover, if one or two very large files are recorded in the data zone, the table of contents area will remain unfilled. Conversely, if there are numerous small data files, the table of contents will fill up before the data zone. In either case, precious storage space is wasted.
In order to read the data at a constant linear track velocity, the storage disk must be rotated at a variable speed, e.g., more rapidly near the ID. Hence, more power is consumed in reading data at the ID than at the OD. In portable, battery-operated storage devices (for example, digital cameras, Palm Pilot(trademark) personal digital assistants, and other similar devices), minimizing power consumption is critical to maximizing battery life. Moreover, the need to accelerate the disk to a relatively high rotational speed increases the amount of time required to access the data.
Conventional storage devices typically store data in fixed block sizes. For example, in DVD optical storage devices each block necessarily contains 32K bytes of data. This can be very wasteful of storage space. Writing a single check mark or fact, for example, normally does not require 32K bytes. Similarly, a xe2x80x9clinking sectorxe2x80x9d containing timing information (described below) must precede the data written during each write session. Linking sectors do not require anywhere near 32K bytes of data. Moreover, file system information must also occupy 32K bytes. Allocating 32K bytes to system data relating to a single file can waste memory space. If, for example, the file or file system data contains only 100 bytes, almost the entire 32K bytes of storage capacity (i.e., 31.99K bytes) remains empty.
Accordingly, there is a need for a storage device and storage medium that is compact and portable, power-efficient, and capable of efficiently storing and transmitting large amounts of data regardless of the size of the individual data files.
A data storage disk in accordance with this invention comprises a writeable area which includes a servo track for guiding a write head. The writeable area includes a writeable system area adjacent an inner boundary of the writeable area; and a writeable data area adjacent an outer boundary of the writeable area. Typically, the writeable system area includes information (attributes) relating to data files stored in the writeable data area. There is no fixed boundary between the writeable system area and the writeable data area.
Initially, there is a blank area between the writeable system area and the writeable data area. As additional file system information is written on the inner diameter (ID) side of the blank area and additional data files are written on the outer diameter (OD) side of the blank area, the blank area shrinks in size. If additional file system information and additional data files continue to be written, ultimately the writeable system area and the writeable data area merge, and the blank area disappears. Whenever that happens, the writeable area will be fully utilized. No storage space will be wasted.
The invention also includes a method of writing data on a data storage disk having a writeable area comprising a writeable system area and a writeable data area, the writeable data area being located radially outward from the writeable system area, the writeable system area and the writeable data area being separated by a blank region. The method includes the steps of writing file system information in a first portion of the blank region located adjacent the writeable system area; and writing a data file in a second portion of the blank region located adjacent the writeable data area. The file system information includes an attribute of the data file. The file system information and data file are written in a direction from the OD of the storage device towards the ID of the storage device.
Writing file system information and data files in this way optimizes the usage of the writeable area, as compared with disk formats that have fixed areas reserved for file system information and data files, respectively, and wherein no additional data can be written once either the file system area or the data area is filled. In this case, there is normally storage space left in the other area and this space is wasted. In a disk formatted in accordance with this invention, the writeable system area and the writeable data area expand towards each other until finally they merge, at which point the entire writeable area is filled.
Using the disk format reduces the power consumption of the disk drive. As discussed above, in conventional systems data is written from ID to OD. In conventional constant linear velocity systems the rotational speed varies with the radius. Hence the rotational speed is the greatest when data is being read from or written near the ID, while the rotational speed is at a minimum when data is being read from or written near the OD. Since data is read from the ID to OD, a high rotational speed is generally required. In the format of this invention the storage device is not required to power up to the highest rotational speed before data may be read. Since lower rotational speed is required for reading data, the power consumption is less compared to conventional systems.
Besides saving power, a storage disk of this invention is available for reading or writing data earlier than conventional disks, i.e., the time for accessing data in the storage disk is reduced. Another advantage of the present invention is that the storage format is flexible. Based upon number and sizes of files, the data and file system zones of the writeable area may be used as necessary. Yet another advantage is that data can be written in plural block sizes rather than the fixed block sizes of conventional systems.
In another aspect, the invention comprises a method of writing data on a data storage disk having a writeable area, the writeable area comprising a first annular region of recorded information and a second annular region of recorded information, the second annular region being located radially outward from the first annular region and being separated from the first annular region by an annular blank area. The method comprises writing first information adjacent an outside edge of the first annular region and writing second information on the inside edge of the second annular region, thereby to reduce the size of the blank area.
In accordance with another aspect of the invention, the writeable area includes error correction code (ECC) blocks of different sizes, for example, a first plurality of ECC blocks of a first size and a second plurality of ECC blocks of a second size, the first size being smaller than the second size. This again increases the utilization of the writeable area, since data which typically occupies less storage space, such as file system attributes and linking sectors, can be written in the smaller ECC block size, resulting in less wasted storage space.
According to still another aspect, the invention comprises a data storage disk comprising a writeable area containing an unwritten servo track wherein a user may write data using a data storage device comprising a write head; and a mastered area containing data formed in conjunction with the manufacture of the disk; wherein the mastered area is located radially outside the writeable area. In many instances, the user will be reading the mastered data (e.g. a music video) and will not be writing data to the disk. In these instances, locating the mastered area radially outward from the writeable area tends to reduce the average rotational speed of a constant linear velocity device, thereby reducing power consumption and increasing the battery life of a portable device. In addition, locating the mastered data radially outward from the writeable area reduces the power consumed and time required in accessing the mastered data. The mastered data may written from the OD of the storage disk toward an ID of the storage disk. The data storage disk may also include a mastered file system zone, wherein the mastered file system zone includes file system objects that are written from the OD towards the ID of the data storage disk.